7.11 导线ab长为1,绕过O点的垂直轴以匀角速w转动 =dfrac (l)(3) 磁感应强度B平行于转轴,如题-|||-7.11所示,-|||-(1)求a、b两端的电势差;-|||-(2)a、b两端哪一点电势高?-|||-B-|||-a b-|||-O-|||-题7.11图